Horizontal and vertical distribution of euphausiids associated with a meso-scale eddy of the Leeuwin Current
Sutton, A.L., Beckley, L.E. and Holliday, D. (2011) Horizontal and vertical distribution of euphausiids associated with a meso-scale eddy of the Leeuwin Current. In: 48th Annual Conference of the Australian Marine Science Association, 3 - 7 July, Fremantle, Western Australia.
Krill (Crustacea: Euphausiacea) is an important component of zooplankton and euphausiids have been studied in many ocean currents and upwelling systems around the world. Off the south west of Australia, euphausiid assemblages were investigated within and around a developing warm core anticyclonic eddy. Twenty two species of euphausiids were recorded, of which two were new records for Western Australia, and several others had southward range extensions. Euphausia recurva (28%), Stylocheiron carinatum (22%) and Pseudeuphausia latifrons (13%) were the most dominant species across the eddy field. Euphausia recurve and S. carinatum were found across most depth ranges, whilst P. latifrons was found in shallower waters and distinguished shelf stations from eddy perimeter/ meander, eddy centre and oceanic stations. The euphausiid assemblage around the perimeter of the eddy was not significantly different from the eddy centre assemblage, highlighting the strong mixing effect of the anticyclonic eddy. Strong vertical distribution patterns were largely driven by calyptopis and furcilia larval stages, with higher concentrations of these larval stages in the upper 80 m of the water column. High concentrations of euphausiids were often located within the mixed layer and in proximity to the deep chlorophyll maximum. Of the environmental variables tested, temperature and, in turn, salinity and dissolved oxygen, and larval fish concentrations were most correlated with euphausiid assemblages. Chlorophyll a and water column depth were weakly correlated with euphausiid assemblages. Tracking water masses over time using surfacedrifter buoys, enabled repeated sampling of euphausiid assemblages, and species composition and proportions of larval stages were found to vary over time. This is the first study to investigate euphausiids within a developing eddy off the south-west coast of Australia.
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|Murdoch Affiliation:||School of Environmental Science|
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